Posted by Steven Fambro (Jesse Hall,Steven Fambro), May 02,1999,23:30 Post Reply  Forum

The EPROM info posted earlier in message 502 is wrong, of course, I'm sure everyone including the staff caught the error :-)

For an AMD AM27C128, Pin 7 is A3 , it is NOT A7. This can be verified by looking at page 3-18 of the AMD memory products data book in the DSL. In the comfort of my office, I could not tell the chip vendor by the logo on the chip, otherwise I would have searched the web, therefore, I had to walk my fat, white ass up to the DSL around 11:00pm and search through the data books. Oh well, I needed the exercise.

The alleged correct pinout makes a debut here (it's also in the AMD mem prod data book in the DSl):

//copied from message 502.html
//modified by Steven P. Fambro
//not for use in a deep-space probe or the like
Pin Function
1 Vpp doesn't appear to matter * See Note below*
2 A12
3 A7
4 A6
5 A5
6 A4
7 A3
8 A2
9 A1
10 A0
11 Q0
12 Q1
13 Q2
14 Gnd
15 Q3
16 Q4
17 Q5
18 Q6
19 Q7
20 \E (Active Low and must be grounded)
21 A10
22 \G (Active Low and must be grounded)
23 A11
24 A9
25 A8
26 A13
27 \PGM (Active Low and must be tied to Vdd)
28 Vcc (Supply Voltage)

*Note from Vpp*

Vpp is used by the EPROM programmer to (you guessed it) program the EPROM. To do this, Pin 1 (Vpp)is raised to 12.5 vdc +/- .5 vdc. For a standard READ mode, which is what our circuit will do, the book reccomends that Vpp be tied to Vcc. This is in the mode select table in the data book on page 3-22.
It appears the pin does not have to be actually tied to *anything* to get the memory contents, but I guess it is good design practice to keep pins from floating. Take this with a grain of salt as I an only a lowly student in this class, and not a TA or anything like that.